I have seen other wild values from the storage probes too. IOP values in the vegative billions or possitive far beyond any sane value. Looks like it make be a number overflowing. I am not sure if the probe is at fault of if the API occasionaly throws a crazy value and the probe just accepts it.

I have written a script I run from the nas sceduler that looks for these extreme values and replaces them with a sane average (so as not to distort the stats too much). If you are interested I will tidy it up a bit and post it here.